This invention relates to an apparatus and method for discharging fluid into a drill string and, in particular, for discharging fluid into the drill string of a rotary-vibratory drill also known as a sonic drill.
It is known to discharge fluid into the drill string of a rotary-vibratory drill as the drill string is being rotated or vibrated into the ground. The fluid helps flush ground cuttings from the bottom of the well bore to the surface, and the fluid maintains a hydrostatic pressure at the bottom of the well bore which restricts ground materials from entering the well bore.
Rotary-vibratory drills impart both rotary and vibratory forces to the drill string. As such, conventional rotary-vibratory drills require a heavy swivel assembly mounted underneath the drill head in order to effectively discharge fluid into the drill string. There is therefore a need for a more efficient apparatus for discharging fluid into the drill string of a rotary-vibratory drill.